Vacuum tube grid construction



Nov. 13, 1934. c. J. KAYKO ET AL VACUUM TUBE GRID CONSTRUCTION Filed April 15 Armmvsr's v i i a WITNESS Patented Nov. 13, 1934 UNITED STATES VACUUM TUBE can) CONSTRUCTION Charles J. Kayko and Paul A. Stoll, Jackson, Mich., assignors to The Sparks-Withington Company, Jackson, Mich., a corporation of Ohio Application April 15, 1931, Serial No. 530,262

1 Claim.

, ploying cylindrical electrodes.

The grid electrode usually consists of fine wire wound in the form of a helix and having a single supporting rod contacting each turn of the helix. The natural requirement of a vacuum tube em- 10 ploying a grid electrode is that the wire forming the grid be of relatively small diameter so as to ofier little resistance to the electron flow between cathode and anode. However, the separate turns of fine wire forming the grid are subjected to mechanical vibration causing plate current modulation or what is commonly known as microphonic action.

It is, therefore, an object of this invention to provide a grid structure for a vacuum tube of comparatively fine wire that will not produce microphonic action.

It is a further object of this invention to produce a grid structure employing only one supporting member, but utilizing additional means for increasing the rigidity of the grid assembly.

Other objects and advantages relate to details of the structure, and will be apparent from the following description, taken in connection with the accompanying drawing in which:-

Figure 1 is a perspective view of a vacuum tube electrode assembly embodying our invention.

Figure 2 is an elevation view of a tube having a portion of the envelope broken away to show the electrodes.

Figure 3 is a sectional view taken along line 33 of Figure 2.

Figure 4 is an elevation view of the grid assembly of our invention.

A conventional heater type vacuum tube 1 is illustrated in Figure 2 having a base 2 and a press 4 for supporting the electrodes. The electrodes are shown to a better advantage in Figure 1. Rising from press 4 are a plurality of rods which serve as supports for the concentrically spaced electrodes as well as electrical connections to the same.

Anode 6 is cylindircal in form and is provided with a flange '7 which may be secured to rod 5. Rod 5 is sealed into press 4 near one end thereof and extends beyond the anode 6. Rod 8 is practically the same length as rod 5 and is positioned near the opposite end of the press as shown.

An insulating member 9 joins rods 5 and 8 at their free ends forming a frame-work for supporting and spacing the remaining electrodes. A rod 10 having its end portion bent parallel to the top of the press provides a support for the lower end of the heater type cathode 11. The upper end of cathode 11 is supported by rod 12 passing through insulator 9.

The cathode, in this instance, is shown comprising a metallic tube 13 provided with an electron-emitting coating 14. The ends of tube 13 are provided with insulating plugs 15 which support a heater element 16 subtended by rods 12 and 25. Electrical connections to the heater are made through rod 10 which is connected to rod 25 and through a cross rod 17 connecting rod 12 to rod 8. Connection to the cathode is made by means of a metallic strip 18 secured at one end to the electron-emitting surface 14 and at the other end to rod 19 sealed in the press.

Grid electrode 20, in this instance the novel feature of this invention, is concentrically positioned with respect to the cathode 11 and anode 6. The grid assembly as shown in Figure 4, comprises a supporting rod 22 to which are secured the grid wires wound in the form of a helix.

Rod 22 is shown in Figure 1 supported at its lower end by a rod 21 sealed in the press and at its upper end by the insulating member 9. Grid wires 23 are preferably welded at each turn to rod 22. In addition, a rod 24 of much smaller diameter than rod 22 is provided diametrically opposite the latter. The grid wires are also preferably welded at each turn to rod 24 so that the rod is electrically and mechanically connected to each turn of the grid.

In practice, we have found that rod 24 need be only from two to three times the diameter of grid wires 23. This construction produces a rigid assembly that is substantially free from mecham cal vibration during normal tube operation. This construction has enabled us to eliminate microphonic action due to plate current modulation set up by vibration of the grid electrode.

It is .to be understood that the foregoing disclosure is merely for the purpose of illustration, and that the invention may be broadly applied to different types of grid'structures, without departing from the spirit and scope of the appended claim.

We claim:

A vacuum tube structure comprising an evacuated bulb including a press, a plurality of metallic members held in said press two of which extend substantially the full length of said bulb and the remainder terminating a short distance from said press, an insulating member mounted upon the free ends of said long metallic members, a cathode and heater therefor positioned was bers, a grid electrode positioned between said 7 anode and cathode comprising a fine wire ,helix secured to a support rod extending beyond the ends thereof and having its lower end secured to another of said short metallic members and its upper end extending through said insulating member, and a second rod of smaller diameter disposed at substantially right angles to the turns of said helix and securedonly thereto for preventing microphonic action in the tube.

CHARLES J. KAYKO. PAUL A. STOLL.

I us) fies, 

